Download Microbiology: A Systems Approach, 2nd ed.

Good physical health
Mental health – if you believe
that you’re not healthy you are
more susceptible to getting sick.
Spiritual – people who are
religious/spiritual tend to be
more upbeat, positive, optimistic
etc…
Pathogenic – disease causing
Opportunistic pathogen – is
generally harmless in its normal
habitat but can become pathogenic
in a host who is seriously
debilitated or has a weak immune
system.
◦ Ex. – pneumocytsis carnii – will cause
pneumonia in AIDS patients
Virulent – Has a very high degree
to cause infection
◦ Ex. – Ebola (80% mortality)
Which is more virulent?
E. coli 0157H7 – pathogen
(found in burgers at Jackin-the-Box)
or
E. coli in Felix’s gut
Note: E. coli in Felix’s gut is an
opportunistic pathogen. Has the ability
to cause an infection but it has to be in
the right conditions/environment like a
sterile site.
The area in which a
microorganism enters the
body. They may be cuts,
lesions, injection sites, or
natural body orifices
◦ Four major pathways

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Skin
Mucous membranes
Placenta
Parenteral route
◦ Contamination – the mere
presence of microbes in
or on the body
◦ Infection – results when
the organism has evaded
the body’s external
defenses, multiplied, and
become established in the
body
◦ Skin
 Outer layer of packed,
dead, skin cells usually
acts as a barrier to
pathogens
 Some pathogens can enter
through openings or cuts
 Others enter by burrowing
into or digesting the outer
layers of skin
◦ Mucous membranes
 Line the body cavities that
are open to the
environment
 Provide a moist, warm
environment that is
hospitable to pathogens
 Respiratory tract is the
most common site of entry
– entry is through the
nose, mouth, or eyes
 Pathogens able to survive
the acidic pH of the
stomach may use the
gastrointestinal tract as a
route of entry
[INSERT TABLE 14.4]
Diseases

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
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Cystic fibrosis
Cancer
Diabetes
Cardiovascular heart disease
(CHD)
Mental diseases (depression)
Alcoholism
Autoimmune (Lupus)
Infection










Cellulitis (pyoderma)
pharyngitis
conjuctivitis
pneumonia
cystitis
otitis media
vaginitis
Colitis
Gastritis
encephalitis
A harmful alteration
of host tissues (arthritis) or
metabolic processes
(Diabetes/hyperglycemia.)

Causation of Disease: Etiology
◦ Study of the cause of disease
◦ Germ theory of disease –
disease caused by infections
of pathogenic
microorganisms
◦ Robert Koch developed a set
of postulates one must
satisfy to prove a particular
pathogen causes a particular
disease
[INSERT TABLE 14.7]
[INSERT TABLE 14.6]
Entry, manifestation,
proliferation of an
infectious agent within a
host.
Infectious agent has to
enter, begin to grow and
continue grow in host
tissues.
Infectious diseases have
been linked to other
Diseases



HPV  cervical cancer
H. Pylori  gastric cancer
Hepatitis B  liver cancer
Microorganism must enter host
tissues.
Microorganism must establish itself
and begin to propagate (grow)
Microorganism must have access to
Nutrients
If one of these three processes is not
met an infection will not manifest
In host tissues.
◦ Ex. – HIV needs nutrients (T4
helper) in order to propagate.
Effects on the body by a
toxin produced by a
biological agent.
Enterotoxin F is produced by
Staphylococcus aureus,
causes toxic shock syndrome.
Difference Between food Poisoning and Foodborne Infecton
Condition
Intoxication by S. aureus
food poisoning)
Infection by Salmonella
(food borne illness)
Time until sick
4 hours
3-14 days
Length (process)
24 hours
until treated
Symptoms
Vomiting
Cramps
Fever
Diarrhea
Dehydration
Tenesmus
Stool sample is taken to look for infectious agent then treated with antibiotics.
A pathogen (infectious agent) or
(more commonly) germ, is a
biological agent that causes disease
or illness to its host.
There are several molecules that
microorganisms produce that allows
invasion into tissues or a means to
exert its pathological affect on the
body.
Virulence factors are molecules
expressed and secreted by pathogens
(bacteria, viruses, fungi and protozoa)
that enable them to achieve the
following:




colonization of a niche in the host
(this includes adhesion to cells)
evasion of the host's immune
response
entry into and exit out of cells (if the
pathogen is an intracellular one)
obtain nutrition from the host.
◦ Pathogenicity – ability of
a microorganism to cause
disease
◦ Virulence – degree of
pathogenicity
 Virulence factors
contributing to an
organism’s virulence





Adhesion factors
Biofilms
Extracellular enzymes
Toxins
Antiphagocytic factors
Virulence factors are very
often responsible for causing
disease in the host as they
inhibit certain host functions.
Pathogens possess a wide
array of virulence factors.
Some are intrinsic to the
bacteria (e.g. capsules and
endotoxin) whereas others
are obtained from plasmids
(e.g. some toxins).
◦ Process by which
microorganisms attach
themselves to cells
◦ Required to successfully
establish colonies within
the host
◦ Uses adhesion factors
 Specialized structures
 Attachment proteins
◦ Toxins
 Chemicals that harm
tissues or trigger host
immune responses that
cause damage
 Toxemia refers to toxins
in the bloodstream that
are carried beyond the
site of infection
 Two types
 Exotoxins
 Endotoxins
The endotoxin is the lipopolysaccharide
(LPS), which is part of the bacterial cell
wall of Gram-negative bacteria.
It is the Lipid A component of the
LPS that has the toxic properties.
The LPS is a very potent antigen and,
as a result, stimulates an intense host
immune response. As part of this
immune response cytokines are
released which cause the fever and
other symptoms seen during disease.
If a high amount of LPS is present then
septic shock (or endotoxic shock) may
result which, in severe cases, can lead
to death.)
Exotoxins, on the other hand, are
actively secreted by some bacteria and
have a wide range of affects including
inhibition of certain biochemical
pathways in the host.
The two most potent exotoxins known to man
are the tetanus toxin (tetanospasmin)
secreted
by Clostridium tetani and the botulinum toxin
secreted by Clostridium botulinum.
Exotoxins are also produced by a range of
other bacteria including Escherichia coli;
Vibrio cholerae (causative agent of cholera);
Clostridium perfringens (causative agent of
food poisoning as well as gas gangrene) and
Clostridium difficile (causative agent of
pseudomembranous colitis).
[INSERT TABLE 14.8]
Microorganisms can producenumerous
enzymes (proteins that break down
substances)

Lipase – breaks down oleic acids
which has many antimicrobial
properties and protects our skin.
◦

Coagulase – coagulates plasma
◦

Produced by Staphylococcus
produced by Staphylococcus aureus
Hyaluronidase – known as “spread
factor.” Hyaluronic acids holds cells
together and Hyaluronidase destroys
the cement that holds the tissues
together.
◦
Produced by Streptococcus pyogenes
and Staphylococcus aureus
◦ Extracellular enzymes
 Secreted by the
pathogen
 Dissolve structural
chemicals in the body
 Help pathogen maintain
infection, invade
further, and avoid body
defenses
The body contains many natural
orders of defense against some of
the common pathogens in the form
of the human immune system and by
some "helpful" bacteria present in the
human body's normal flora.
Figure 14.1
◦ Skin (largest organ of the
body)
◦ Mucous membranes –
openings to body (ears,
mouth, anus, urethra)
Figure 14.2
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
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Sneeze
Cough
Lacrimation (tears)
Sweat
Ear wax
Salivation
Defecation
Peristalsis – movement
of food material in the
intestinal tract
Figure 14.3
•
•
•
•
•
•
•
•
Sebaceous secretions and
specialized glandsantimicrobial
Lysozyme in tears
Lactic acid and electrolyte
concentrations of sweat
Skin’s acidic pH and fatty
acid content
HCl in the stomach
Digestive juices and bile in
the intestine
Semen- antimicrobial
chemical
Acidic pH in the vagina
Complement cascade –
entire immune system is
turned on
Functions – neutralizes
viruses, enhances
phagocytosis, damages
plasma membrane, can
destroy (lyse)
microorganism



At least 26 blood proteins that work in
concert to destroy bacteria and certain
viruses
Cascade reaction
Three different pathways that all yield similar
end results
◦ Classical pathway
◦ Lectin pathway
◦ Alternative pathway
Antiviral properties – good in
fighting cancer and viruses
Body produces minute amounts
Interferes with transcription
and translation of mRNA
•
•
•
•
•
Interferon (IFN): involved against viruses, other microbes, in
immune regulation and intercommunication
Three major types
– Interferon alpha
– Interferon beta
– Interferon gamma
All three classes produced in response to viruses, RNA, immune
products, and various antigens
Bind to cell surfaces and induce changes in genetic expression
Can inhibit the expression of cancer genes and have tumor
suppressor effects
Figure 14.18
Normal flora – bacteria or
plants. These organisms are
with you for your entire life.
They keep infectious
pathogens in check.
Natural resistance –resistance
you’ve acquired throughout
your life (adult) Resistance
acquired from mother (child.)


Immunology: the study of all features of the body’s second
and third lines of defense
Healthy functioning immune system is responsible for:
◦ Surveillance of the body
◦ Recognition of foreign material
◦ Destruction of entities deemed to be foreign
White blood cells must distinguish self from
nonself cells
Evaluates cells by examining markers on their
surfaces
Figure 14.4
White blood cells
◦ B lymphocytes
◦ T lymphocytes